Dannyalcatraz said:While it was a ring to rule the world, it, like many magic items, had lesser powers. Its invisibility was perfectly controllable- put on, take off, Miyagi-san.
If JRRT had written his story as if this particular rule applied, neither Frodo nor Bilbo would have been able to use the Invisibility effect at all.
Non-Invisible Hobbits = Dead Hobbits in a short, short story.
I didn't actually use the One Ring as an example, but Gandalf's ring of power/fire. Its mentioned in the Simarillion that it and the other lesser power rings only function if you were well, powerful enough.
Basically, no living Man (maybe Aragorn....) of the post-Lotr era could use Gandalf's ring yet in ages past, Random Joe Blow soldier of Man would've been able to but of course said random soldier probably could solo a Nazgul by himself.